Great Britain recently raised its terror alert to "severe" following reports that al Qaeda was plotting new attacks.

But Britain may be facing an even greater threat from within -- one the British government helped to create.

CBN News recently traveled to London to interview a number of leading Islamic radicals who have settled there with the full knowledge of the British government.

All Eyes on London

Just one year before attempting to blow up an airliner over Detroit, Christmas Day bombing suspect Umar Farouk Abdulmutallab studied engineering at University College London.

During his stay there, he networked with known Islamic radicals. Security sources believe he may have linked up with al Qaeda.

Abdulmutallab is just one of many Islamic terrorists with ties to London. Some live there with help from the state.

One example is Yasser al-Sirri, who faces a death sentence in Egypt.

Then there is Anjem Choudary. To date, he has not been charged with terrorism, but his pro-jihad views have led some to call him Great Britain's most hated man.

"Many people love the idea of jihad, you know?" Choudary told CBN News. "And they want to engage in it."

A radical Islamist can find a little bit of everything in London. Ex-jihadists, current jihadists, "wannabe" jihadists: they're all there. So how did this happen?

During the 1980s and 1990s, British authorities granted asylum to a number of Islamic terrorists wanted in their home countries.

"All of this happened under the assumption that if you allowed these people to operate in London, if you allowed them to do whatever they wanted to do, they would not be attacking Britain," terrorism expert Peter Neumann explained.

Neumann is author of the book Old and New Terrorism and heads the International Centre for the Study of Radicalization in London.

"The government, quite cynically, thought that whatever happened in other countries, whatever these people were plotting in other countries, was of no concern to the British government," he added.

Policy Backfires

On July 7, 2005, explosions proved the British government's open door strategy horribly wrong, as al Qaeda-linked terrorists killed 52 people in a series of bombings against London's mass transit system.

One year later, London was the staging ground for a massive al Qaeda plot to blow up 10 transatlantic airliners.

"Only then did the policy change," Neumann said. "However, the seeds of the radical Islamists' activity had already been sown."

Yasser al-Sirri has lived in London since 1994. In Egypt, he belonged to a terrorist organization led by al Qaeda's second-in command, Ayman al-Zawahiri. In 1993, he was found guilty of participating in a failed assassination plot against Egypt's then-prime minister and sentenced to death.

His recent interview with CBN News marked his first appearance on an American television network.

"The British government knows about my activities, my situation," al-Sirri said. "Everything is clear and I have done nothing to break the law."

The British government locked al-Sirri up in 2001 on terrorism charges. He was found not guilty and later released, but American officials still want to get their hands on al-Sirri.

In 2005, he was found guilty in a U.S. federal court of assisting terrorist mastermind Omar Abdel Rahman, the notorious "blind sheikh" behind the 1993 World Trade Center bombing.

False Accusations?

Both the U.S. and Egypt have tried to extradite al-Sirri from Britain for years. He declares he is innocent.

"Many times the American government uses the wrong people for spies or to get intelligence information," al-Sirri claimed. "Some people do business with the FBI, CIA and give them wrong information and sometimes the wrong decision is made."

Al-Sirri didn't help his cause in 2008 when he was photographed walking on a London street with Abu Qatada, al Qaeda's spiritual leader in Europe.

Qatada received asylum in London in 1993 and collected welfare benefits for years. He is now in prison and awaiting deportation to Jordan, where he has been convicted on terrorism charges.

"There was a permissive environment to some extent," said Oxford-based terrorism expert Mahan Abedin. "There was the issue of a lot of foreigners, foreign fighters for instance, and foreign ideologues basing themselves here in London and finding a receptive audience."

Aaad al-Faqih is wanted in his native Saudi Arabia for allegedly seeking to overthrow the Saudi regime.

CBN News recently conducted an off-camera interview with al-Faqih in his London home.

He was designated by the U.S. and U.N. as a global terrorist in 2004 for alleged links to al Qaeda but maintains his innocence. Al Faqih says he meets with British government officials regularly and that they respect his work.

He believes there will be more confrontation between the West and the Muslim world, including terrorist attacks "even bigger than in 2001."

British officials have pushed to deport men like al-Faqih and Yasser al-Sirri back to their home countries. But the European Union and a number of British judges have blocked these efforts over human rights concerns.

"Over years, perhaps decades, a whole sub-culture had grown up," Neumann observed. "And to get to grips with that only through law enforcement and intelligence is very difficult. This subculture of jihadism still exists."

In April 2008, Britain's then home secretary said that British intelligence was monitoring some 2,000 individuals, as well as 200 radical Islamic networks and 30 active terrorist plots.

The British government banned Anjem Choudary's group, Islam4UK, last month under the country's counter-terrorism laws.

Choudary calls for Islamic Sharia law to be enforced in the United Kingdom. His group praised the 9/11 hijackers as "the magnificent 19."

"There is a huge amount of support for people like sheikh Osama bin Laden and Ayman al-Zawahiri [among British Muslims]," Choudary told CBN News.

A Ticking Time Bomb?

Choudary -- who collects welfare benefits from the state -- says his group is a non-violent political and ideological movement. But several former members have been convicted on terrorism charges.

"There are many youth out there who do contact us and do come to our talks and they have other ideas," Choudary said. "And we can make sure that those energies are channeled through discussion, dialogue, interaction. But if you take us out of the picture, then you have a very volatile situation."

"It's not a threat. It's a warning. It's a reality check," he added.

Abedin said things have improved significantly in London since 2005 and the British government has taken important steps to battle radicalism among young Muslims.

"The permissive environment that prevailed prior to July 7, 2005 is no longer the case," he said. "Radical preachers like Omar Bakri Mohammed, like Abu Hamza, for instance, have departed the arena. They've either been deported, expelled, or imprisoned.

But others like Anjem Choudary walk the streets of London as free men.

"I think that the British government is sitting on a tinderbox, you know, full of dynamite" he said. "And they have the matches in their hand and they're being very flippant."

"They're not dealing with it properly," Choudary continued. "It could all blow up in their face and it could be a very vicious situation."

Erick Stakelbeck

CBN News Correspondent

Erick Stakelbeck is a sought after authority on terrorism and national security issues with extensive experience in television, radio, and print media. Stakelbeck is a correspondent and terrorism analyst for CBN News. Follow Erick on Twitter @Staks33.